Method and arrangement for diminishing noise in vacuum tubes



July 25, 1933- w. SCHAFFER I 1,919,593 METHOD AND ARRANGEMENT FOR DIMINISHING NOISE IN VACUUM TU BES Original Filed Oct. 28, 1924 P/MSFAR/l/JTER I I I I I Patented July 25, 1933 nits sir w tenses WALTER sonerrnn, or nmamn; Gnu-MANY. nssie nei r0 'rnrinsunnnn ensurinsormrr run nnnn'rnosn rnnnennrnrn VMI'I" nnsonn nnxsnn Her-rune, or BERLIN, GERMANY, A conronnrion or unmen Q l MErI-IonANn ARRANGEMENT non nnurmsi-irne noise in vacuum TUBES Original application filed octoberes, 1924, Serial ua zeeaes, now ratenene. 1,765,542, dated June 24, 1930, and in Germany December-'18, 1923. Divided and this application. filed Julyl, 1927. "Serial This invention relates to method and apparatus for diminishing and eliminating the note caused by the use of, alternating current for heating the cathode of thermionic tubes and is for the same purpose asthe method and means set forth in my copending application Serial No. 746,268filed Oct. 28, 1924, Patent No. 1,765,542, June 2 1980, of which this is a divisional application.

The object of this invention is to provide an arrangement whereby thenote caused by the alternating cathode heating current is compensated or eliminated. This is accomplished by using an anode current derived from an alternating current of the --same frequency asthe cathode heating current.

Another object of the invention isto provide means whereby the relative amplitude and the phase relation of the direct, current anode current and the grid'cathode current can be regulatechin such a manner that the note caused by the alternating currentiin the grid cathode circuit can be totally eliminated. q f

Other-objects will be apparent fromthe following description and claims when taken with the accompanying drawing in which 2.

tation illustrating my invention.

-E lectr on tubes whose cathodes are heated a The single figure is a schematic represenby alternating current ordinarily} cause a tone of the alternating current frequency and also of double the frequency in the output circuit. It is all the same whether the electron tube is used as an amplifier'or as an os'cillationgenerator. In the latter case i the generated oscillation is modulated by the tones caused by the heating current. Means for diminishing 'theset ones caused by the heating current are known. A very suitable. arrangement is, for instance, to ar-- range an ohmic resistance in parallel to theheating filament and to use the middle of this resistance as they IF-point, that is, the connection contact ofthe grid circuit and .of the anode circuit. That component of the heating current note which has the same frequency as theheating current can becompletelyeliminated by this connection. V On the otherhand, a heating current note of. the double frequency remains. This note is based upon ,twor causes Firstly, the heating of the filament and consequently-the electron emission-slightly pulsates in the. rhythm of double the heating current irequency, even whenranwalternating current of as high as 500 periods per second is employed. Secondly, the potential ofthe filamentwith respect to the grid is'varied with the double frequency, as the two halves of thle filament mustbe regarded as symmetrica.

a'rectifie'd alternatingcurrent, the anode current-itself. also containsa component of thedouble frequency of the employed rectified alternating current, and this frequency is-fl-particularly strong when atwo phase parted rectifier. So. the anode current heating current,i the anode alternating our- ,In case the anode voltage is generated by V rent and --'tl 1e heating current have thesame frequency. The components caused by the anodecurrent and heating current will. strengthen; or weaken one another accord:

ing to the difierence of phases of these two currents. This fact is'employedby the present invention according to which the phases .of the disturbing components caused by the heating voltage and by the anodevoltage are compulsively and constantly adjustedduringithe working'of the electron tube, so

thatthe two components act against one an- ,otherpand; weaken one another. Referring to. the single figure the m'itting tube m acts upon theoscillatory cirtrans-v suit" I which comprises inductance L and capacitance V. Inductance L has a portion connectedzinthe output circuit of tube a and also a 'portion'in the input circuit of tube (a to give the .necessaryffeed back to cause sustained oscillations. -lShe generator c acting thro'ugh the transformer (Z supplies'the heatingalternating current. The

secondary ot transformer disconnected to the filament-of the tube a to which theresistancele is connected inparallel; and the middle of'this resistance is, as known, the. K-point. The generator 9 produces a two-phased alternating current of the same frequency as that of the heating current generator 0. This current is transformed by transformer 7b and rectified by the double rectifier Thealternating current generators 0 and g are compulsively connected to one another by the couplingA, and it is all the same whether they have a common shaft or not. The coupling A contains an arrange-- mentby means of which the rotors of both generators can'be adjusted to any desired relative angle. The maximum turning angle corresponds to a phase displacement of 360 between the alternating currents of the two generators. Any phase angle between heating current and anode current can be adjusted by means of this arrangement. 7 The grid-cathode circuit iscoupled to the direct current anode circuit, for instance, inductively, in such a way that the alternating current component of the double work-' ing frequency which the a-node'di'rect current contains, is superimposed on the normal grid direct current or alternating current. Thereby the disturbing component which is brought in by the heating current, is compensated to a certain extent, or more exactly, it is equalled to the component of the anode note. The right phase for which the disturbing note is a minimum so that itv will completely disappear atsuitable coupling, maybe adjusted, as mentioned above, by regulating the Variable coupling of the generators.

In this case the anode circuit contains'an inductance m and the grid circuit an inductance coil or. V The inductances m and a are coupled to one another by avariable coupling, the sense of which can be reversed.

The condenser 0 bridges over the coupling coil'a for the high frequency flowing through the grid circuit of the tube transmitter. The arrangement is adjusted in such'a way that first thecoils m and n are short-circuited and'the phase between the working anode current and the heating current :is adjusted to make the disturbing note a minimum by suitably regulatingthe cou-. pling A; then the short-circuit is removed from the coilsj m and a, and then the dis-.

turbing "note is farther diminished orcompletely eliminated by suitably adjusting the I pling, v v

In some cases sense ofcou-pling and the coeflicient of couit "may be appropriate to adjust thephases of the disturbing-components of the anode current and the'grid current only partly by means of the coupling "A ofthe'generators g and 0 by which often 0111 an inaccurate re ulation is carried out;

For the accurate regulation of the phases, further impedances are inserted in the anode circuit, or grid circuit, by means of ;which an accurate phase: displacement. is

possible also possible to displace the phases of the two disturbing components by arranging any other resistances in the anode circuit or direct current; grid. circuit;

In each case the currents are adjusted to that point of phase relationship at which the disturbing note which for instance may be tested by means of an auxiliary detector circuit (not shown) has the least strength.

Having described my invention and the operation thereof I claim l. The method of diminishing the alternating current hum from thermionic Valves the anode cathode circuit and the cathode heating circuit of which are energized from an alternating current source which comprises, supplying," the cathode heating cir cuit with alternating current, supplying the anode cathode circuit with'currcnt derived,

gether with the capacity. Of'course, it is from alternating current of the-same 'fre- V quency,'roughly adjusting the phase relation of saidtcurrents to oppose each other, couplingthe direct current anode'cathode cir-' cuit to the'di'rect current grid cathode circuit, adjusting the magnitude of thetwo currents-to be numerically equal to each other, and finely adjusting the phase relation of said. currents tooppose and com: pensate each other;

2. The method of diminishing the alter nating current hunrjfrom thermionic valves the anode cathode circuit and the cathode heating circuit of which .are operated from an alternating current source which comprises, supplying the cathode heating. circuit with alternating current, supplying the anode cathode circuit with current derived from alternatlng current ofthe same frequency, adjusting the phase "relationof said currents to oppose eachother, and coupling; the direct current anode cathode circuit ,to

the grid cathode circuit,

:3. The method of diminishing the alter.-

nating currenthumfrom thermionic "valves 7 when the anode cathode circuit and the oathode heating circuit thereof. are operated from an alternating current source, whichicon 'sists-of supplying the cathode heating c1rcuit with alternating current, supplying the I anode cathode circuit with current derived from alternating current" of the same frequency, adjusting the phaserelationzof said currents to oppose each other, coupling the direct current anodeycathode circuit'to-the "gridcathode circuit, and adjustingthe magof the twocurrents so that they will be nitude ofthe two currents to be numerically equal. 1

4. The method of diminishingthe alternating current hum from thermionic valves the anode cathode circuit and the cathode. heating, circuit or" which are operated from an alternating current source which comprises supplying the cathode heating circuit,

equal to each other.

5. In radio apparatus a thermionic valve having anode cathode and grid electrodes, a

direct current anode cathode circuit, a direct current grid cathode circuit, a source of current for said anode cathode circuit derived from alternating current, a source of alternating current of the same frequency for heating the cathode of said valve, and means including a coupling between said direct current circuits for adjusting the. phase relation and the relative magnitude of said currents. 7' l 6. In radio apparatus a thermionic valve having anode cathode and grid electrodes, a V

direct current anode cathode circuit, adirect current grid-cathode circuit, means foretecluding radio frequency currents from'said dlrect current anode cathode circuit, asource of current for said anode cathode circult derived from' alternating current, a source of alternating current of thesame frequency for heating the cathode of said valve, atuned impedance in said direct current anode cathode circuit,-a tuned impedance in said direct current grid cathode circuit variably coupled to said first named impedance, and means for excluding radio frequency current from the impedance in said direct current I grid cathode circuit.

7. An arrangement for supplying anode potential, and heating current to the cathode of a'thermionic valvehaving high frequency input and output circuits including, a source ofalternating current for the cathode heating circuit, a circuit-for supplying rectified alternating current to the anode circuitfrom .an alternating current source, and coupling means between the input circuit and the anode supply c1rcu1t for pro-.

ducing a hum frequency voltage in saidfinput circuit and means for adjusting the i phase and amplitudeof said voltage to substantially reduce the hum. caused by alter nating currents.

, i WALTER SCHAFFER. 

